GB887272A - Improvements in photographic silver halide emulsions - Google Patents

Abstract

Compounds are described having the general formula <FORM:0887272/IV (b)/1> wherein R is hydrogen or methyl, D is ethylene or o-phenylene, D1 completes a thiazolidine, tetrahydrothiazine or benzthiazoline nucleus and Q is=O or, when R is H and D is o-phenylene, Q may be =NH. The benzene rings may be substituted with chlorine, bromine, methyl, ethyl, methoxy or ethoxy substituents. Preferably D represents the group -(CH2)n-CH(R1)- where n is 1 or 2 and R1 is H or a carboxy group (or water-soluble salt, e.g. an alkalimetal, triethylamine, triethanolamine or pyridine salt, thereof) in ortho position to the N-atom. Compounds wherein Q is oxygen may be prepared by reacting a ketone of the formula R-CO-R2 (where R2 is a b -carboxyethyl or o-carboxyphenyl group, the benzene ring of which may have substituents) with an o-aminobenzene-thiol or with a mercaptan of the formula HS-(CH2)n-CH(R1)-NH2, (III) which latter may be in the form of its hydrochloride or hydrobromide. Thus cysteine hydrochloride or b -mercapto-ethylamine is reacted with levulinic acid or phthalaldehydic acid, homocysteine hydrochloride is reacted with phthaldehydic acid, and o-aminobenzenethiol is reacted with phthaldehydic acid. Compounds wherein Q is =NH, R is H and D is o-phenylene are prepared by condensing o-cyanobenzaldehyde with o-amino-benzenethiol or with a compound of formula III above such as cysteine hydrochloride. Specification 649,545 is referred to.